This invention relates to integrated circuit modules of the type in which one or more integrated circuit chips are mounted on an interconnect member such that multiple input/output pads on each chip are connected to corresponding input/output pads on the interconnect member.
In the above type of integrated circuit module of the prior art, the interconnect member has included a substrate which holds a single chip or which holds multiple chips. This substrate can be made of ceramic or silicon or epoxy glass. Thousands of patterned conductive signal lines are provided within and/or on top of the substrate; and, those signal lines include input/output pads which are arranged in a pattern that matches the input/output pads on each chip. One example of such a prior art interconnect member is described in U.S. Pat. No. 4,721,831 entitled "Module for Packaging and Electrically Interconnecting Integrated Circuit Chips on a Porous Substrate, and Method of Fabricating Same" by H. Vora issued Jan. 26, 1988. There, in FIG. 1, reference numeral 10 identifies the interconnect module and reference numeral 12 identifies the chips; and in FIG. 2, reference numeral 21 identifies the input/output pads on the interconnect module.
Now, a technical problem which somehow needs to be solved when fabricating integrated circuit modules of the above type is how to align the input/output pads on each chip with the corresponding input/output pads on the interconnect module while the chips are being attached to the interconnect module. This is a difficult problem because the input/output pads typically have small dimensions (e.g.-ten mils), are large in total number (e.g.-one hundred), and are blocked from view by the chip when the chip is placed on top of the interconnect member. However, if the input/output pads on a chip get misaligned with the corresponding input/output pads on the module, all electrical signals (including data signals, control signals, power and ground signals) will be misrouted to and from the chip; and, the resulting structure will be completely inoperable.
In the prior art, this problem of how to align the input/output pads on a chip to the input/output pads on an interconnect module was overcome by using specialized alignment machines. But, those machines are very complex and thus are very expensive. One such machine, for example, called a "M-9" from the Research Devices Division of the American Optical Corporation, provides an infrared light beam to "see" through the chip and thereby view when the input/output pads on the chip and the interconnect module are in line. But, this machine costs over $100,000. Another machine, called a MRSI-503M from Micro Robotics Systems, Inc. provides an optical probe with dual optical paths which fits between the chip and the substrate as they are positioned over each other so that their input/output pads can be viewed and lined up. But, this machine also costs over $100,000. Further, the above costs are for manually operated versions of both machines; automated versions cost over $200,000.
Accordingly, a primary object of the present invention is to provide an improved integrated circuit module that includes novel microscopic physical features on the chips and on the interconnect module which enable their input/output pads to be self-aligned without any alignment equipment.